***Disclaimer: I'm doing refinishing for hire***
Overview:
There are multiple types of finishes. Broadly speaking there are surface finishes and there are treatments. Surface finishes (aka as coatings) are a distinct, separate material phase from the underlying structure. Examples include polymer systems like Cerakote, bluing, parkerizing, electrochemically deposited metals metals like chrome and nickel, composites like electroless nickel, and thin film/hard coatings like boron nitride or titanium nitride. Treatments include gas or salt bath nitriding and carbonitriding, case hardening, and boriding.
What brought this one was a pile of emails and PM's asking about finishes and which finish should be used. So, I'm going to attempt to do some comparison and contrast to help out.
First off is the answer to the question "which should I use?" My personal favorite is electroless nickel. Yes, I'm offering EN, but we also do polymers, boriding, and bluing. I make more money and have less headaches with bluing and polymers. Boriding is neat, and I think it is superior to FCN, but it has downsides too.
So why Electroless Nickel? Here are a list of advantages:
1. Corrosion resistance. The only thing that comes close is polymer coatings with silanes (what we offer).
2. Wear resistance. FCN and boriding come close.
3. Works on all metallic substrates (steel, stainless, aluminum, titanium)
4. Is additive.
5. Doesn't exhibit "throw" like hard chrome
6. Isn't on the EPA hit list like hard chrome
7. Can be self lubricating by the addition of wear resistant particles (like SiC) or lubricating particles (like PTFE or HBN)
8. Can be "alloyed" with other metals to meet specific aesthetic or performance criteria - we add tungsten/molybdenum to increase hardness while maintaining corrosion resistance.
9. Adhesion is excellent, better than HC.
10. Some can be blackened.
11. Can be applied, stripped, and reapplied easily.
Downsides:
1. Application is arty. How you apply (temperature, pH, etc) will affect the coating greatly.
2. Can be costly to apply.
This is my favorite firearm finish. And specifically, I like ones that have low phosphorus and medium hexagonal boron nitride. It looks like frosted stainless steel, and is not slippery like the PTFE finishes. It's harder than chrome, more corrosion resistant, and has great adhesion. Is slightly less corrosion resistant than the high phos versions. For ARs, I like the upper, lower, and BCG finished in the low phos, BN finish blackened as desired. Blackening can be done with sulfuric acid or citric acid.
Next up, is my second favorite finish: polymers. Will post up on this ASAP, for now, some pics.
Now some thoughts to hopefully get the people who PM'ed me to ask the questions here:
1. FCN is problematic dimensionally. It was designed for low alloy, low carbon steels. Not 4xxx series or stainless steel. The benefits are far less in alloy steel.
2. Diamond like carbon is excellent for holster wear, but not much else.
3. No finish will allow you to run w/o lubrication for extended periods of time, in spite of marketing efforts.
4. The most corrosion resistant finish out there is electroless nickel, without additives and with high phos.
5. Polymers don't adhere well to stainless steel because of the underlying oxide layer. Which is the reason the gun in the above pics looks like it does.
6. The best finish for Al frames is electroless nickel.
7. Anodizing doesn't do much of anything for wear resistance and nothing for strength.
8. HC over FCN is a great way to have the HC peel off.
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Originally Posted by montanadave
